Commit d7880812b3594d3c6dcbe3cfd71dabb17347d082

Authored by Thomas Gleixner
1 parent c7788792a5

idle: Add the stack canary init to cpu_startup_entry()

Moving x86 to the generic idle implementation (commit 7d1a9417 "x86:
Use generic idle loop") wreckaged the stack protector.

I stupidly missed that boot_init_stack_canary() must be inlined from a
function which never returns, but I put that call into
arch_cpu_idle_prepare() which of course returns.

I pondered to play tricks with arch_cpu_idle_prepare() first, but then
I noticed, that the other archs which have implemented the
stackprotector (ARM and SH) do not initialize the canary for the
non-boot cpus.

So I decided to move the boot_init_stack_canary() call into
cpu_startup_entry() ifdeffed with an CONFIG_X86 for now. This #ifdef
is just a temporary measure as I don't want to inflict the
boot_init_stack_canary() call on ARM and SH that late in the cycle.

I'll queue a patch for 3.11 which removes the #ifdef if the ARM/SH
maintainers have no objection.

Reported-by: Wouter van Kesteren <woutershep@gmail.com>
Cc: x86@kernel.org
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Showing 2 changed files with 16 additions and 12 deletions Side-by-side Diff

arch/x86/kernel/process.c
... ... @@ -277,18 +277,6 @@
277 277 }
278 278 #endif
279 279  
280   -void arch_cpu_idle_prepare(void)
281   -{
282   - /*
283   - * If we're the non-boot CPU, nothing set the stack canary up
284   - * for us. CPU0 already has it initialized but no harm in
285   - * doing it again. This is a good place for updating it, as
286   - * we wont ever return from this function (so the invalid
287   - * canaries already on the stack wont ever trigger).
288   - */
289   - boot_init_stack_canary();
290   -}
291   -
292 280 void arch_cpu_idle_enter(void)
293 281 {
294 282 local_touch_nmi();
... ... @@ -5,6 +5,7 @@
5 5 #include <linux/cpu.h>
6 6 #include <linux/tick.h>
7 7 #include <linux/mm.h>
  8 +#include <linux/stackprotector.h>
8 9  
9 10 #include <asm/tlb.h>
10 11  
... ... @@ -112,6 +113,21 @@
112 113  
113 114 void cpu_startup_entry(enum cpuhp_state state)
114 115 {
  116 + /*
  117 + * This #ifdef needs to die, but it's too late in the cycle to
  118 + * make this generic (arm and sh have never invoked the canary
  119 + * init for the non boot cpus!). Will be fixed in 3.11
  120 + */
  121 +#ifdef CONFIG_X86
  122 + /*
  123 + * If we're the non-boot CPU, nothing set the stack canary up
  124 + * for us. The boot CPU already has it initialized but no harm
  125 + * in doing it again. This is a good place for updating it, as
  126 + * we wont ever return from this function (so the invalid
  127 + * canaries already on the stack wont ever trigger).
  128 + */
  129 + boot_init_stack_canary();
  130 +#endif
115 131 current_set_polling();
116 132 arch_cpu_idle_prepare();
117 133 cpu_idle_loop();